In a liquid crystal display, a plurality of gate lines (GL) is sequentially selected and a positive voltage is applied to the selected gate line (GL) while a negative voltage is applied to the other gate lines (GL). For example, if one gate line GL is circuit-shorted to a negative voltage line through a defect, overcurrent flows into transistors of a driver circuit when a positive voltage is applied to the gate line GL. Since such overcurrent flowing into the transistors may overheat or damage the transistors, there is a need to turn off the transistors.
As one of methods for detecting overcurrent of transistors, there has been proposed a method for detecting a voltage drop due to on-resistance of transistors and determining that overcurrent flows into transistors if the detected voltage drop exceeds a predetermined voltage.
However, in a method of turning off the transistors when the overcurrent flows into the transistors, no overcurrent is detected when the transistors are turned off, and then, when a normal gate line GL not circuit-shorted is selected, a driver circuit is normally operated. This may result in repeated overcurrent flown in the gate line GL and hence overheating and damage of the transistors.